Thermostable and O2-Insensitive Pyruvate Decarboxylases from Thermoacidophilic Archaea Catalyzing the Production of Acetaldehyde

Faisal Alharbi; Thomas Knura; Bettina Siebers; Kesen Ma

doi:10.3390/biology11081247

Thermostable and O₂-Insensitive Pyruvate Decarboxylases from Thermoacidophilic Archaea Catalyzing the Production of Acetaldehyde

Biology (Basel). 2022 Aug 22;11(8):1247. doi: 10.3390/biology11081247.

Authors

Faisal Alharbi¹, Thomas Knura², Bettina Siebers², Kesen Ma¹

Affiliations

¹ Department of Biology, University of Waterloo, Waterloo, ON N2L3G1, Canada.
² Molecular Enzyme Technology and Biochemistry (MEB), Environmental Microbiology and Biotechnology (EMB), Centre for Water and Environmental Research (CWE), Faculty of Chemistry, University of Duisburg-Essen, 45141 Essen, Germany.

Abstract

Pyruvate decarboxylase (PDC) is a key enzyme involved in ethanol fermentation, and it catalyzes the decarboxylation of pyruvate to acetaldehyde and CO₂. Bifunctional PORs/PDCs that also have additional pyruvate:ferredoxin oxidoreductase (POR) activity are found in hyperthermophiles, and they are mostly oxygen-sensitive and CoA-dependent. Thermostable and oxygen-stable PDC activity is highly desirable for biotechnological applications. The enzymes from the thermoacidophiles Saccharolobus (formerly Sulfolobus) solfataricus (Ss, T_opt = 80 °C) and Sulfolobus acidocaldarius (Sa, T_opt = 80 °C) were purified and characterized, and their biophysical and biochemical properties were determined comparatively. Both enzymes were shown to be heterodimeric, and their two subunits were determined by SDS-PAGE to be 37 ± 3 kDa and 65 ± 2 kDa, respectively. The purified enzymes from S. solfataricus and S. acidocaldarius showed both PDC and POR activities which were CoA-dependent, and they were thermostable with half-life times of 2.9 ± 1 and 1.1 ± 1 h at 80 °C, respectively. There was no loss of activity in the presence of oxygen. Optimal pH values for their PDC and POR activity were determined to be 7.9 and 8.6, respectively. In conclusion, both thermostable SsPOR/PDC and SaPOR/PDC catalyze the CoA-dependent production of acetaldehyde from pyruvate in the presence of oxygen.

Keywords: Saccharolobus solfataricus; Sulfolobus acidocaldarius; archaea; ethanol fermentation; hyperthermophiles; pyruvate decarboxylase; pyruvate:ferredoxin oxidoreductase.

Abstract

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